JP2827566B2 - Alignment apparatus, exposure apparatus, and method of manufacturing semiconductor device using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positioning apparatus and an exposure apparatus suitable for manufacturing semiconductor devices, and a method for manufacturing semiconductor devices using them, and more particularly, to a receiving apparatus synchronized with a reticle having a conjugate relationship with a wafer. Signals from a plurality of alignment marks having different line widths provided on the wafer surface for relative alignment with the means are measured a plurality of times or spatially, and the measurement based on the three-dimensional structure of the alignment marks The present invention relates to an alignment apparatus, an exposure apparatus, and a method of manufacturing a semiconductor device using the alignment apparatus and the exposure apparatus, which can be performed with high accuracy by capturing an error.

[0002]

2. Description of the Related Art In recent years, with the demand for miniaturization of a circuit pattern of a semiconductor device, an exposure apparatus for manufacturing a semiconductor device has been required to have a highly accurate relative alignment between a reticle and a wafer.

[0003] Among the conventional alignment methods in an exposure apparatus, various methods have been proposed which utilize diffracted light from a grating mark on a wafer surface.

For example, a method using a heterodyne optical system (The Japan Society of Applied Physics Fall 1989, Proceedings 50 Fall 29a-L)
-2 (magome etc.)) and a method using image information (Japanese Unexamined Patent Application Publication No.
-206706). JP-A-2-2-2 of the latter
In an alignment method using image information proposed in JP-A-06706, a wafer mark for alignment (for alignment) is formed by forming a groove or a step on a wafer surface. Then, a transparent thin film photosensitive material (resist) for performing exposure on the surface is applied to the entire surface of the wafer including the wafer mark.

FIG. 19 is a schematic view of a main part of a positioning device proposed in Japanese Patent Application Laid-Open No. 2-206706.

In FIG. 1, an electronic circuit pattern on a reticle R surface illuminated by exposure light from an illumination device IL is projected on a wafer W surface mounted on a wafer stage ST by a projection lens 1 in the same manner as in a conventional exposure device. The image is reduced and projected and transferred.

At this time, alignment is performed by using a light beam having a wavelength different from the exposure light emitted from the linearly polarized He-Ne laser (wavelength λ) 2 as an acousto-optic device (AO device) 26.
The AO element 26 controls the amount of light traveling toward the mirror 21 and completely shuts off the light in a certain state, for example. The light is reflected by a mirror 21 whose rotation can be controlled in two axes, and is incident on an F-θ lens 22. The light is reflected by the polarization beam splitter 5, and the λ / 4 plate 6, the lens 7, the mirror 8, and the projection lens 1 illuminate the wafer mark GW 'on the surface of the wafer W with an incoherent light beam.

FIGS. 20A and 20B are a plan view and a schematic sectional view of the wafer mark GW 'of FIG. In the figure, RES indicates a resist, and WEF indicates a wafer substrate. LW is the grating pitch of the wafer mark.

At this time, the illumination light is applied to a pupil plane of an optical system composed of the projection lens 1,
An incoherent effective light source as shown in FIG.
The light amount is controlled by the element 26 and the rotation of the mirror 21 is controlled to form the mirror 21 effectively.

Here, X2 and Y2 in FIG. 21A are coordinates on the pupil plane, and represent the distribution of illumination light incident on the wafer W surface. The illumination distribution is based on the wafer mark G
The rotation mirror 21 and the AO element are controlled so as to illuminate only the range corresponding to the zero-order light when W 'is regarded as a diffraction grating. The shaded area indicates the illumination range. Dotted lines indicate so-called zero-order light 190, first-order light 191, 2
The order light 192 and the order light 193 are shown. FIG. 21 (C)
Is a distribution of diffracted light when the wafer W is used as a diffraction grating.

A light beam from the wafer mark GW 'on the surface of the wafer W passes through the projection lens 1 and then passes through a mirror 8, a lens 7, a λ / 4 plate 6, a polarizing beam splitter 5, a lens 9, and a beam splitter 10 in sequence. An aerial image of the wafer mark GW 'is formed at the position A.

The aerial image is further converted to a Fourier transform lens 23.
The angle of the reflected light from the wafer mark GW 'on the wafer by the stopper 32 is ± sin ^-1 (λ
/ LW), and transmits the wafer mark G to the solid-state imaging device 11 via the Fourier transform lens 24.
The image of W 'is formed. In FIG. 21B, a hatched portion is a transparent portion of the stopper 32. That is, as shown in FIG. 6, zero-order light is incident on the wafer W, and ± first-order light is taken in.

On the other hand, a light beam from a light source 12 such as an LED, which emits a wavelength different from the wavelength from the He-Ne laser 2, is condensed by a condenser lens 13, and a reference mark GS 'formed on the surface of a reference mask 14 is formed. Lighting.
Then, the light beam from the reference mark GS ′ is reflected, and the LED 1
An aerial image of the reference mark GS ′ is formed on the A plane via the beam splitter 10 configured to reflect the light beam from the He.Ne laser 2 and transmit the light beam from the He—Ne laser 2. Thereafter, the aerial image on the surface A is formed on the surface of the CCD 11 similarly to the image of the wafer mark GW '.

The reference mark GS 'has a pitch LW of the wafer mark GW' on the CCD 11 surface as shown in FIG.
And a lattice pattern having a pitch LS ′ set to be the same as the pitch. In FIG. 22A, a hatched portion is a transparent region and the others are opaque regions.

Next, the positioning method shown in FIG.
This will be described with reference to the flowchart of FIG.

First, in the initial state in STEP 0, the positional relationship between the reticle R and the positioning device (for example, the CCD 11) has already been aligned, and the coordinate origin on the reticle R and the center of the reference mark GS 'have already corresponded. attached. The wafer W is made of He with an accuracy on the order of several micrometers.
When the laser beam from the Ne laser 2 is irradiated, the wafer stage ST is driven so that the wafer mark GW 'is already present at a predetermined position in the alignment device so that the wafer mark GW' is imaged at a predetermined position on the imaging device 11. doing.

In STEP 1, the LED light source 12 is irradiated to form a reference mark image GS 'on the imaging device 11.
The formed image is as shown in FIG. The A / D converter 27 converts the electric signal of the imaging device 11 into 2
After the replacement with the dimension array, a processing window ES is provided and y
Pixels are integrated in the direction, and a one-dimensional array diagram 22 (C) is obtained, FFT (Fast Fourier Transform) is performed with the center of the screen as the origin, the amount of deviation from the center of the screen corresponding to the fundamental frequency is measured, and fixed to the alignment device. The position between the reference mark GS ′ and the imaging device 11 is determined.

In STEP 2, a He-Ne laser 2 is irradiated, and a wafer mark image is formed on the imaging device 1 through the above-described path.
1. The formed image is as shown in FIG. Then, after the electric signal of the imaging device 11 is replaced by the A / D converter 27 into a two-dimensional array, the processing window E
S is provided, pixels are integrated in the y direction in FIG. 20 (C), and a one-dimensional array diagram 20 (D) is obtained.
(Fast Fourier Transform) is performed to measure the amount of deviation from the center of the screen corresponding to the fundamental frequency, and the position of the wafer mark GW ′ and the imaging device 11 is determined.

In STEP 3, the positional deviation between the alignment device and the wafer W is converted into coordinates with the reticle R, and the alignment controller 29 drives the wafer stage ST to a predetermined position during exposure to complete the alignment. .

[0020]

The image of the alignment mark (wafer mark) on the wafer surface is distorted by the influence of uneven coating of the resist applied on the surface and the asymmetry of the three-dimensional structure of the alignment mark. It is known to be observed. This causes a measurement error, so-called damascene, when detecting the position of the alignment mark, which causes a reduction in the alignment accuracy.

Particularly, in a process of applying a resist on a wafer surface after a metal compound is vapor-deposited by sputtering or the like in a semiconductor element manufacturing process, serious damage caused by unevenness due to uneven coating of the resist near an alignment mark is a serious problem. It has become.

On the other hand, damasare caused by the resist layer in the step of depositing the metal compound is rarely caused by the wavelength dependence of the refractive index of the thin film interference due to the high reflectance of the metal compound, and is caused by unevenness in application of the resist. The influence of geometric optics is greater.

FIGS. 24A and 24B are optical path diagrams showing the phenomenon at this time. FIG. 24A is a cross-sectional view near the alignment mark for aligning the wafer.

In the figure, WEF is a wafer, RES is a resist,
AIR is the air layer. RAY1 and RAY2 indicate the optical path of one ray of the observation light. ALM is a groove of the alignment mark. The refraction directions of the light rays RAY1 and RAY2 are largely changed by a local change (undulation shape) of the resist surface RESa.

When the reflectivity of the wafer surface WEFa is high, it is considered that the interference effect between the reflected light on the resist surface RESa and the reflected light on the wafer surface WEFa is sufficiently smaller than the geometrical optical effect.

FIG. 24B is an explanatory view of the distribution of the light intensity of the observation light corresponding to FIG. Resist surface RESa
The alignment mark image is observed to be shifted laterally due to the local change of the mark. This cannot be removed by whitening the illumination light or optimizing the wavelength of the illumination light.

On the other hand, it is known that there is a certain relationship between the shape of the wafer mark and the undulation of the resist surface. According to LEStillwagon and RGLarson, etc., the wider the line width of the wafer mark, the worse the flatness of the resist surface becomes,
Conversely, it is said that the narrower the line width, the better the flatness of the resist surface. (SPIE, Vol, 920, P312 ~ 320,198
8).

Here, the flatness P of the resist surface is defined by the following equation.

Now, the resist thickness is set at W at the center of the wafer mark.
D1, when the resist thickness at a position far from the wafer mark is WD2, and the step thickness of the wafer mark is WD3

[0030]

(Equation 1) It is.

From this, it can be seen that the flatness P of the resist surface becomes maximum at the limit where the line width of the wafer mark becomes zero.

As described above, the narrower the line width becomes, the more the line width becomes smaller.
The flatness of the resist surface is increased, and the local undulation near the wafer mark is reduced. That is, a positioning signal with a small damascene amount can be obtained.

FIG. 25 is an explanatory diagram of the distribution of the light intensity of the observation light corresponding to the line width of the wafer mark. If the line width is wide as shown in FIG. 7A, the flatness of the resist surface RESa deteriorates, and the damascene amount Δx ₁ with respect to the center position x ₀ is large as shown in FIG.

On the other hand, when the line width is reduced as shown in FIG. 4C, the flatness of the resist surface RESa is improved, and as shown in FIG. 4D, the damascene amount Δx _{2 with} respect to the center position x ₀ is reduced. It is smaller than in FIG.

Since the resist on the wafer is applied by spin coating, the application condition depends on the distance from the center of the wafer on the wafer. That is, when the angular velocity at the time of spin coating is ω, the centrifugal force F at the radius r with the origin at the center of the wafer is given by F∝rω ² and acts as an external force on the resist. This causes uneven application of the resist. Therefore, it is known that the damage caused by uneven coating is also a function of the radius r. (Autumn 1990, Proceedings of the Japan Society of Applied Physics, 27p-Z
G-16, Kazuhiro Yamashita et al.) When the measured amount is f (r), f (r) = m × r + f0 ‥‥‥‥ (1). Here, f0 is a unique displacement amount of the wafer, where m is called a wafer magnification, and m depends on the unevenness of resist coating as described above, that is, m (w) = a × w + m0 ‥‥‥‥ (2) m0 is the actual shrinkage of the wafer due to thermal effects and the like in the semiconductor device manufacturing process, and is hereinafter referred to as true wafer magnification.

In order to improve the measurement accuracy (to improve s / n), the distance r of the wafer mark in the wafer from the center of the wafer
It is desired to increase the number of parameters as a statistic in such a point as greatly different from the above.

In general, the lower limit of the line width of the alignment mark is determined by the resolution of the exposure apparatus, and is such a line width that satisfies the alignment accuracy required for alignment, that is, the local undulation of the resist surface can be ignored. There is a problem that a wafer mark with a narrow line width cannot be realized.

The present invention uses a plurality of wafer marks composed of a plurality of alignment marks having different line widths to determine the amount of damaging at the center position at the time of alignment based on the undulation shape of the resist surface near the alignment mark on the wafer surface.
An alignment apparatus, an exposure apparatus, and a semiconductor device using the same, which can be corrected by using signals obtained at the same time or at a time interval therefrom to perform high-accuracy alignment between the wafer and the imaging means. The purpose is to provide a method.

[0039]

SUMMARY OF THE INVENTION A positioning apparatus according to the present invention is a positioning apparatus for arranging receiving means synchronized with a reticle and a wafer via an optical system and performing relative positioning between the two. A plurality of wafer marks composed of a plurality of alignment marks having different line widths are formed on the wafer surface, and a resist is applied on the surface,
Recording means for recording a relational expression between a line width of the alignment mark and a displacement amount of position measurement due to a change in an incident position of the light beam to the receiving means due to the undulating shape of the resist surface is provided. A plurality of alignment marks forming the illuminated wafer mark are guided by the optical system on the receiving means surface at the same time or at a time interval, and the receiving means simultaneously synchronizes the position information of the plurality of alignment marks. Alternatively, extraction is performed at a time interval, the extraction is performed for the plurality of wafer marks, and the position caused by the undulation of the resist surface is obtained by using the obtained positional information and the relational expression recorded in the recording means. A shift error is statistically obtained, and relative positioning between the wafer and the receiving unit is performed with reference to the position shift error.

In addition, in the present invention, the plurality of alignment marks are composed of diffraction gratings, and are arranged in the same direction as or orthogonal to the alignment direction, and one of the plurality of alignment marks is the same. It is characterized in that a plurality of line width marks are arranged at the same pitch in the alignment direction.

The exposure apparatus of the present invention optically detects the positions of a plurality of relief marks on a resist-coated wafer and, based on the position detection, converts the pattern on the wafer into a circuit pattern of a mask. Position with respect to
In an exposure apparatus for exposing a resist covering a pattern on the wafer via the circuit pattern, the plurality of relief-shaped marks form first and second alignment patterns each having a different line width w ₁ and w _2. And optically detecting the positions of the first and second alignment patterns of one of the plurality of relief marks at the same time or at a time interval. Position data x
₁ , x ₂ , a line width and position data (w ₁ , x ₁ ) of the _first alignment pattern, and a line width and position data (w ₂ , x ₂ ) of the _second alignment pattern
And a function x (w) of the line width w is calculated based on
Means for determining the position data x ₀ when the line width w = 0 according to (w) with respect to the plurality of relief-shaped marks, wherein the statistical value of the plurality of position data obtained at this time is The above-mentioned alignment is performed on the basis of this.

Further, the above-described positioning device, exposure device,
And a method of manufacturing a semiconductor device using them, optically detects the positions of a plurality of relief marks on a resist-coated wafer, and based on the position detection, the pattern on the wafer is used as a mask. When aligning with a circuit pattern, exposing a resist covering a pattern on the wafer through the circuit pattern, and then developing a resist on the wafer to manufacture semiconductor elements from the wafer, Are formed of a plurality of linear patterns, and the first and second alignments of the plurality of linear patterns of one relief mark having different line widths w ₁ and w _2. Each position of the pattern is optically detected at the same time or at a time interval, and first position data x corresponding to the first alignment pattern is detected based on the position detection.
₁ and second position data x ₂ corresponding to the second alignment pattern are formed, and the line width and position data (w ₁ , x ₁ ) of the _first alignment pattern and the line width of the second alignment pattern A function x (w) of the line width w is obtained based on the position data (w ₂ , x ₂ ) and the line width w is calculated by the function x (w).
= Performed for relief-like mark the plurality of determining the position data x ₀ of 0, it is characterized by performing the positioning based on the statistical value of the plurality of position data obtained at this time .

[0043]

FIG. 1 is a schematic view of a main part of an optical system according to a first embodiment of the present invention.

In the same figure, the electronic circuit pattern on the reticle R surface illuminated by the exposure light from the illumination device IL on the wafer W surface mounted on the wafer stage ST by the projection lens 1 in the same manner as the conventional exposure device. The image is reduced and projected and transferred.

At this time, the alignment is performed by causing a light beam having a wavelength λ different from the exposure light emitted from the linearly polarized He—Ne laser 2 to enter the acousto-optic device (AO device) 26. Controls the amount of light going to the mirror 21, and completely shuts off the light in a certain state, for example. The light is reflected by a mirror 21 whose rotation can be controlled in two axes, and is incident on an F-θ lens 22.

After that, the illumination range is spatially limited by a field stop SIL disposed on a plane optically conjugate with the wafer W, and then the light is incident on the polarization beam splitter 5.
The light is reflected by the polarization beam splitter 5, and the λ / 4 plate 6, the lens 7, the mirror 8, and the projection lens 1 illuminate the wafer mark GW on the wafer W surface with an incoherent light flux.

FIG. 2 is an explanatory diagram of the wafer mark GW of FIG. As shown in FIG. 2A, the wafer mark GW is composed of a plurality of alignment marks Wa (Wa1 to Wa3) having a line width D of a relief diffraction grating and different pitches LW. Then, as shown in FIG. 2B, each alignment mark Wa (Wa1 to Wa3) of the wafer mark GW is formed.
Are arranged in different areas on the scribe line SL. SIMP is a pattern region of a semiconductor process.
In this embodiment, a plurality of such wafer marks GW are arranged on the wafer surface.

That is, the wafer mark GW has a relief shape (3
(Dimensional shape) and three alignment marks Wa1, Wa2, and Wa3 having different line widths. (In the figure, three alignment marks Wa1 to Wa
Although three is shown, this number may be any number. ) The line width of the alignment mark Wa1 is D1, and the pitch is LW1.
And a plurality of them are arranged at regular intervals in the alignment direction (X direction). The line width of the alignment mark Wa2 is D
2. The pitch is LW2 and the alignment mark Wa3
Has a line width of D3 and a pitch of LW3. Like the alignment mark Wa1, a plurality of lines are arranged at equal intervals in the alignment direction. (In the present embodiment, a single isolated pattern (FIG. 13) may be used instead of the diffraction grating pattern as the alignment mark.) At this time, the illumination light is an optical light constituted by the projection lens 1, the lenses 22 and 7. On the pupil plane of the system, for example, an incoherent effective light source as shown in FIG.
1 is effectively formed by controlling the rotation. This is not performed in this embodiment, but is effective in the case of ± first-order light incidence and ± first-order light extraction.

Here, X2 and Y2 in FIG. 3A are the coordinates of the pupil plane, and represent the distribution of the incident angle of the illumination light with respect to the wafer plane.

The illuminance distribution on the pupil plane at this time is a range corresponding to the zero-order light when the wafer mark GW is regarded as a diffraction grating, and the rotating mirror 21 and the AO element 26 are illuminated only in that range. Controlling. In FIG. 3A, a hatched portion indicates an illumination range. Also, ranges 30, 31, 32, and 33 surrounded by dotted lines are so-called pitches LW1 of 0,
1, 2, and 3rd-order diffracted lights are shown.

FIG. 3C shows the distribution of diffracted light when the wafer mark GW is a diffraction grating. FIG. 4 is an explanatory diagram of the illumination range on the wafer W surface. As shown in the figure, the field stop (FIG. 1, SIL) is arranged so as to illuminate only a part RIL in the lattice pattern of the alignment marks Wa1, Wa2, and Wa3.

The light beam from the alignment mark Wa1 of the wafer mark GW on the surface of the wafer W passes through the projection lens 1, and then sequentially passes through the mirror 8, the lens 7, the λ / 4 plate 6, the polarizing beam splitter 5, the lens 9, and the beam. An aerial image of the alignment mark Wa1 is formed at the position A via the splitter 10. Other alignment marks Wa2
The same applies to Wa3.

The aerial image is further converted to a Fourier transform lens 23.
Of the light reflected from the wafer mark GW (alignment marks Wa1, Wa2, Wa3) by the stopper 25 having three types of stoppers 25a, 25b, 25c, respectively, and the angle on the wafer is sin ⁻¹ (λ / LWi) i. = 1,2,3 only, and the Fourier transform lens 2
An image of the wafer mark GW is formed on the solid-state imaging device 11 as a receiving unit via the imaging device 4.

That is, FIG. 5 is an explanatory view of the stopper 25, and the hatched portion in the drawing is the transmission range. As shown in FIG. 5, each of the 0-order lights is incident on the wafer mark GW, and each of the ± 1st-order diffracted lights is taken in.

In the stopper 25 of this embodiment, the transmission range (shaded portions in FIGS. 5A, 5B, and 5C) has a transmission range corresponding to the optical axis depending on the type of the alignment mark (Wa1 to Wa3). Drive control is performed by the stopper control device 30 so as to be positioned above.

In the present embodiment, the stopper 25 shown in FIG.
(A), (B), (C) three stoppers 25a, 2
5b, 25c are provided, and alignment marks Wa1,
Wa2 and Wa3 are used.

In this embodiment, three types of transmission ranges may be provided for one stopper, and the corresponding transmission ranges may be used for each alignment mark.

On the other hand, a light beam from a light source 12 such as an LED that emits a wavelength different from the wavelength from the He-Ne laser 2 is condensed by a condenser lens 13 to form a reference mark GS formed on a reference mask 14. Lighting.

The reference mark GS has a pattern as shown in FIG. Then, the light beam from the reference mark GS is reflected, the light beam from the LED is reflected, and He-Ne is reflected.
An aerial image of the reference mark GS is formed on the surface A via a beam splitter 10 configured to transmit a light beam from the laser 2. Thereafter, the aerial image on the surface A is formed on the surface of the CCD 11 similarly to the image of the wafer mark GW.

As shown in FIG. 7A, the reference mark GS is composed of a diffraction grating having a pitch LS set to be the same as the pitch LW3 of the alignment mark Wa3 of the wafer mark GW on the CCD 11 surface. . Note that FIG.
In (A), the shaded area is a transparent area, and the others are opaque areas.

Next, the positioning method according to the present embodiment will be described with reference to the flowchart of FIG.

On the wafer W, a plurality of areas (for example, 32 shots) called shots having a circuit pattern exposed by the same reticle and a wafer mark GW are provided.
Existing. FIG. 9 shows each shot on the wafer W of this embodiment, and each shot is numbered for convenience.

In the initial state in STEP 0, reticle R
And the position of the alignment device (for example, the CCD 11) has already been aligned (synchronized), and the coordinate origin on the reticle R and the center of the reference mark GS have already been associated.

In STEP 1, the LED light source 12 is irradiated to form an image of the reference mark GS on the image pickup device 11.
The formed image is as shown in FIG. Therefore, after the electric signals of the imaging device 11 are replaced by a two-dimensional array by the A / D converter 27, a processing window ES is provided by the image processing device 28, and pixels are integrated in the y direction in FIG. 7C, an FFT (Fast Fourier Transform) is performed with the center of the screen as the origin, the amount of deviation ΔS from the center of the screen corresponding to the fundamental frequency is measured, and the reference mark GS fixed to the positioning device is The positional relationship with the imaging device 11 is determined. Thereby, the illumination of the LED 12 is completed.

When the wafer W is irradiated with the He—Ne laser 2 in STEP 2, the alignment make Wa 1 of the wafer mark GW in the first (n = 1) shot is displayed on the imaging device 11 with an accuracy of the order of several micrometers. The wafer stage ST is driven so that an image is taken at a predetermined position, and the wafer stage ST already exists at a predetermined position in the positioning device.

In step 3, the current shot number n is N
(For example, 12). Shot number n
When N is N, the process moves to STEP7.

If the shot number n is not n = 1 in STEP 4, the wafer stage ST is held in the alignment device for a predetermined distance (the alignment mark Wa3 of the shot number n-1 and the alignment mark Wa1 of the shot number n). (The relative position difference), and the stopper control device 30 changes the stopper 25 to the stopper 25a in FIG. Irradiate He-Ne laser 2,
Through the above path, the n-shot alignment mark W
The image of a1 is formed on the imaging device 11. The formed image is as shown in FIG.

Then, after the electric signals of the imaging device 11 are replaced by a two-dimensional array by the A / D converter 27, a processing window EW1 is provided by the image processing device 28, and the pixels are integrated in the y direction in FIG. The array is arranged, FFT (Fast Fourier Transform) is performed with the center of the screen as the origin, and each shift amount Δ1 ⁿ from the center of the screen corresponding to the fundamental frequency is measured and stored.

In STEP 5, the wafer stage ST is driven by a predetermined distance (design relative position difference between the alignment marks Wa1 and Wa2), and the stopper control device 30 moves the stopper 25 through the stopper 25b shown in FIG. The part is changed to be located on the optical axis. He-Ne
The light from the laser 2 is irradiated to form an image of the alignment mark Wa2 on the imaging device 11 via the above-described path.
The formed image is as shown in FIG. Therefore, after the electric signals of the imaging device 11 are replaced by a two-dimensional array by the A / D converter 27, a processing window EW2 is provided by the image processing device 28, pixels are integrated in the y direction in FIG. FFT (Fast Fourier Transform) is performed with the center of the screen as the origin, and each shift amount Δ2 ⁿ from the center of the screen corresponding to the fundamental frequency is measured and stored.

In STEP 6, the wafer stage ST is driven by a predetermined distance (design relative position difference between the alignment marks Wa2 and Wa3), and the stopper control device 30 moves the stopper 25 through the stopper 25c shown in FIG. The part is changed to be located on the optical axis. He-Ne
The light from the laser 2 is irradiated, and an image of the alignment mark Wa3 is formed on the imaging device 11 through the above-described path.
The formed image is as shown in FIG. Therefore, after the electric signals of the imaging device 11 are replaced by a two-dimensional array by the A / D converter 27, a processing window EW3 is provided by the image processing device 28, pixels are integrated in the y direction in FIG. FFT (Fast Fourier Transform) is performed with the center of the screen as the origin, and each shift amount Δ3 ⁿ from the center of the screen corresponding to the fundamental frequency is measured and stored.

At STEP 7, the deviation amounts Δ1 ⁿ , Δ2 ⁿ ,
The wafer magnification at the alignment mark of each line width is calculated from Δ3 ⁿ and the position in each alignment mark.
At this time, as shown in FIG. 9, since the alignment marks Wa1, Wa2, and Wa3 of the wafer mark GW are arranged in the 図 direction, the radius r in the equation (1) is calculated by replacing the projected component on the ξ axis. . Then, the amount of damaging of the wafer magnification due to the unevenness in application of the resist is calculated from the line width and the wafer magnification. FIG. 11 shows the relationship between the line widths of the alignment marks Wa1, Wa2, and Wa3 and the wafer magnifications m1, m2, and m3.

In FIG. 11, the X mark is a measured value. The alignment mark is obtained by a relational expression (a linear approximation as a first-order approximation in the present embodiment, which is a first-order approximation) between each measured value, a wafer mark GW, and a deviation amount of the measured value due to uneven resist coating and a line width. The true wafer magnification m0 in the state where the line width of Wa is zero is obtained by the least square method. That is, the position of the true position of the wafer mark GW with respect to the imaging device 11 is determined.

In STEP 8, the true displacement between the positioning device and the wafer W is converted into coordinates with the reticle R, and the positioning control device 29 calculates a predetermined position of the entire surface of the wafer W at the time of exposure. The wafer stage ST is driven to the exposure position calculated at the time of exposure of the exposure shot to complete the alignment.

In this embodiment, the alignment marks Wa1 to Wa3 having different line widths are measured at different times with a time interval. For example, the alignment marks are divided into two groups, and the alignment marks Wa1 and Wa2 are simultaneously aligned. Each alignment mark may be arranged so that the mark Wa3 can be measured at another time. Alternatively, an alignment mark may be formed so that all can be observed at the same time, and observation may be performed at the same time.

Further, in this embodiment, the amount of damaging of the wafer magnification strongly depends on the manufacturing process of the semiconductor device, and there is no remarkable difference between the wafers manufactured at the same time. Accordingly, only the first wafer of the same period is subjected to the damascene correction and the alignment mark Wa1 is obtained.
Is determined and stored after the difference between the calculated value and the true wafer magnification is determined.
It is also possible to measure the misalignment between shots only for the alignment mark Wa1 on the wafer and to correct the wafer magnification to predict the amount of misalignment of the entire surface of the wafer while keeping the damaging amount of the wafer magnification unchanged without changing the wafer magnification. Good.

In this embodiment, alignment marks having different pitches LW and line widths D are used at the same time.
As shown in FIG. 26, the pitch LW is set to the same pitch LW1, and only the line width D is changed to the alignment mark Wb1,
Wb2 and Wb3 may be used.

In this case, since the pitch LW as the diffraction grating is the same, the stopper control device 30 shown in FIG. 1 is not required, and one stopper 25a shown in FIG. . At this time, the relationship between the wafer magnifications m1b, m2b, m3b and the true value in each of the alignment marks Wb1, Wb2, Wb3 is, for example, a quadratic function as shown in FIG. Therefore, in this embodiment, the measurement value sequence m1b, m2b, and m3b are quadratic approximated by the least squares method, and the limit of the line width D0 is set as the true wafer magnification.

Also, the line width is made the same, and FIG.
When the pitch LW is changed as shown in (C), the cross-sectional shape (FIGS. 28 (B) and 28 (C)) becomes the same as the case where the line width has changed effectively. Therefore, the same effects as described above can be obtained.

Further, in this embodiment, the alignment marks Wa1, Wa2,
The case where Wa3 is measured and thereafter the wafer moves to the next wafer mark is shown.

In another embodiment of the present invention, each shot is measured for the alignment mark Wa1, then each shot is measured for the alignment mark Wa2, and further, each shot is measured for the alignment mark Wa3. The sequence of obtaining the value of the wafer magnification or the like by performing the statistical processing described above can be similarly applied.

FIG. 12 is a schematic view of a main part of an optical system according to a second embodiment of the present invention.

In the same drawing, an electronic circuit pattern on a reticle R surface illuminated by exposure light from an illumination device IL is projected onto a wafer W surface mounted on a wafer stage ST by a projection lens 1 in the same manner as a conventional exposure device. Reduced projection and exposure transfer.

At this time, alignment is performed by causing a light beam having a wavelength (λ) different from the exposure light, which is emitted from the linearly polarized He—Ne laser 2, to enter an acousto-optic device (AO device) 26. The AO element 26 controls the amount of light traveling toward the mirror 21 and completely shuts off the light in a certain state, for example. The light is reflected by a mirror 21 whose rotation can be controlled in two axes, and is incident on an F-θ lens 22.

After that, a stopper SIL is placed on a plane optically conjugate with the wafer W, and the illumination range is spatially limited there, and then light is incident on the polarization beam splitter 5. Then, the light is reflected by the polarizing beam splitter 5, and λ
The alignment mark MW1 of the wafer mark MW on the surface of the wafer W is illuminated with an incoherent light beam by the / 4 plate 6, the lens 7, the mirror 8, and the projection lens 1.

FIG. 13 is an explanatory diagram of the wafer mark MW of FIG. As shown in the figure, the wafer mark MW has a line width D.
Alignment marks MW1, MW2, M
It consists of W3. In addition, three alignment marks M
W1, MW2 and MW3 have respective line widths D1, D2 and D3.
And is arranged on the scribe line SL.

At this time, the illumination light is applied to the pupil plane of the optical system composed of the projection lens 1, the lenses 22 and 7, by controlling an incoherent effective light source so as to have a circular shape, for example, by controlling the amount of light by the AO element 26 and controlling the mirror 21. It is formed effectively by controlling the rotation. Then, the rotating mirror 21 and the AO element are controlled so as to illuminate only that range.

The luminous flux from the wafer mark MW on the surface of the wafer W is sequentially passed through the projection lens 1, mirror 8, lens 7, λ / 4 plate 6, polarizing beam splitter 5, lens 9, and polarizing beam splitter 10 by the imaging lens 31. An image of the wafer mark MW is formed on the imaging device surface 11.

On the other hand, the light beam from the LED light source 12 radiating a wavelength different from the light from the He-Ne laser 2 is condensed by the condenser lens 13 and
It illuminates the reference mark MS formed on the surface.
The reference mark MS has a pattern as shown in FIG.

In the figure, the hatched portions are light transmitting portions. Then, the light beam from the reference mark MS is reflected, the light beam from the LED 12 is reflected, and the light beam from the He-Ne laser 2 is transmitted through the beam splitter 10 configured to transmit the light beam from the He-Ne laser 2. An image of the reference mark MS is formed.

Next, the positioning method in this embodiment will be described with reference to the flowchart of FIG.

On the wafer W, a plurality of areas (for example, 32 shots) called shots having a circuit pattern exposed by the same reticle and a wafer mark GW are provided.
Existing. FIG. 16 shows shots on the wafer W in this embodiment, and the shots are numbered for convenience.

STEP 0, reticle R as an initial state
The position of the positioning device (for example, the imaging device 11) has already been aligned, and the coordinate origin on the reticle R and the center of the reference mark MS have already been associated.

In STEP 1, the LED light source 12 is irradiated to form an image of the reference mark image MS on the image pickup device 11. The formed image is as shown in FIG. Therefore, the electric signal of the imaging device 11 is converted into the A / D converter 2
7, a processing window ES <b> 2 is provided by the image processing device 28, pixels are integrated in the y direction of FIG. 14B, a one-dimensional array (FIG. 14C), and the center of the screen is set. One-dimensional pattern matching is performed as the origin, the deviation ΔS of the center of the reference mark MS from the center of the screen is measured, and the reference mark MS fixed to the positioning device is measured.
The positional relationship between the image and the imaging device 11 is determined. This gives L
The lighting of the ED 12 is finished.

In STEP 2, when the wafer W is irradiated with the He—Ne laser 2 with an accuracy of the order of several micrometers, the alignment mark MW 1 of the wafer mark MW in the first (n = 1) shot is changed to the image pickup device 11. The wafer stage ST is already driven at a predetermined position in the positioning apparatus so as to be imaged.

In step 3, the current shot number n is N
(For example, 13). Shot number n
When N is N, the process moves to STEP7.

If the shot number n is not n = 1 in STEP 4, the wafer stage ST is held in the positioning device for a predetermined distance (the alignment mark MW3 of the shot number n-1 and the alignment mark MW1 of the shot number n). Drive).

The He-Ne laser 2 is irradiated, and an n-shot image of the alignment mark MW1 is formed on the imaging device 11 through the above-described path. The image formed is shown in FIG.
(A). Therefore, after the electric signals of the imaging device 11 are replaced by a two-dimensional array by the A / D converter 27, a processing window EW1c is provided by the image processing device 28, and the pixels are integrated in the y direction in FIG. (D)
Then, one-dimensional pattern matching is performed with the center of the screen as the origin, and the shift amount Δ1c of the center of the mark from the center of the screen is measured and stored.

In STEP 5, the wafer stage ST is driven by a predetermined distance (design relative position difference between the alignment marks MW1 and MW2). The He-Ne laser 2 is irradiated to form an n-shot image of the alignment mark MW2 on the imaging device 11 via the above-described path. The formed image is as shown in FIG. Then, after the electric signals of the imaging device 11 are replaced by a two-dimensional array by the A / D conversion device 27, the processing window EW2c is processed by the image processing device 28.
17, the pixels are integrated in the y direction in FIG. 17 to obtain a one-dimensional array diagram 17E. One-dimensional pattern matching is performed with the center of the screen as the origin, and the shift amount Δ2c of the center of the mark from the center of the screen is measured and stored.

In STEP 6, the wafer stage ST is driven a predetermined distance (design relative position difference between the alignment marks MW2 and MW3). The He-Ne laser 2 is irradiated, and an image of the alignment mark MW3 is formed on the imaging device 11 via the above-described path. The image formed is shown in FIG.
(C). Therefore, after the electric signals of the imaging device 11 are replaced with a two-dimensional array by the A / D converter 27, a processing window EW3c is provided by the image processing device 28, and the pixels are integrated in the y direction in FIG. (F)
Then, one-dimensional pattern matching is performed with the center of the screen as the origin, and the amount of deviation Δ3c of the center of the mark from the center of the screen is measured and stored.

In STEP 7, the respective deviation amounts Δ1c, Δ2
c, Δ3c and the position within each alignment mark, the wafer magnification m1c at the alignment mark of each line width,
m2c and m3c are calculated. The amount of damaging of the wafer magnification due to the unevenness in application of the resist is calculated from the line width and the wafer magnification. Line width D (D1, D2, D3) of alignment marks MW1, MW2, MW3 and wafer magnifications m1c, m2
FIG. 18 shows the relationship between c and m3c.

In FIG. 18, the X mark is a measured value. The alignment mark is obtained by a relational expression (a linear approximation is used as a first approximation in the present embodiment as a first-order approximation) of the deviation of the measurement value due to each measurement value, the wafer mark MW, and the unevenness of the resist coating and the line width. The true wafer magnification m0 in the state where the line width is zero is obtained by the least square method. That is, the position of the true position of the wafer mark MW with respect to the imaging device 11 is determined.

In STEP 8, the true displacement between the positioning device and the wafer W is converted into the coordinates of the reticle R, and the positioning control device 29 calculates a predetermined position of the entire surface of the wafer W at the time of exposure. The wafer stage ST is driven to the exposure position calculated at the time of exposure of the exposure shot to complete the alignment.

In this embodiment, the alignment marks MW1 to MW3 having different line widths are measured at different times with a time interval. For example, the alignment marks are divided into two groups, and the alignment marks MW1 and MW2 are simultaneously aligned. Each alignment mark may be arranged so that the mark MW3 can be measured at another time. Alternatively, an alignment mark may be formed so that all can be observed at the same time, and the observation may be made at the same time.

Further, in this embodiment, the amount of damaging of the wafer magnification strongly depends on the manufacturing process of the semiconductor device, and there is no remarkable difference between the wafers produced at the same time. Therefore, the above damascene correction is performed only on the first wafer made at the same time, and the difference between the calculated value of the alignment mark MW1 and the true wafer magnification is determined and stored. Alignment mark M
The wafer magnification of W1 is fixed without changing the amount of damage.
The deviation between shots may be measured only for the alignment mark MW1 on the wafer, and the magnification of the wafer may be corrected to predict the amount of positional deviation on the entire surface of the wafer.

As described above, according to the present embodiment, it is possible to calculate the amount of damaging caused by uneven coating of the resist from the line width of the alignment mark and the measured position value without using the alignment method. Can be removed.

The present invention can be applied to the following positioning device. (A) By using a Fresnel zone plate type wafer mark to narrow the illumination range of the alignment marks having different line widths, measurement is performed when plural alignment marks are effectively removed or not. An apparatus that obtains true position information by obtaining the limit where the line width of the alignment mark is zero by a similar method based on the difference between the values. (B) An apparatus that scans a laser beam by driving an illumination side or a wafer, and temporally measures a wafer mark image or an optical signal from the wafer as an electrical signal based on the result. (C) An apparatus used in Example 2 as a dark field instead of a bright field.

[0107]

According to the present invention, a plurality of wafer marks composed of a plurality of alignment marks having different line widths are formed on the wafer surface as described above, and position information from each of these alignment marks is simultaneously or temporally separated. This is performed for each wafer mark, and by using each position information obtained at this time, the amount of damascene based on the undulation shape of the resist surface caused by the alignment mark is statistically corrected, and unnecessary noise light is corrected. Can be removed, and a highly accurate alignment between the wafer and the exposure apparatus main body (receiving means) can be achieved.

Further, according to the present invention, even in the above-mentioned optical heterodyne method, the position of zero line width can be predicted by measurement using a plurality of types of line width marks without depending on the specific method. Thus, it is possible to achieve an alignment device having the same effect as described above.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a main part of an optical system according to a first embodiment of the present invention.

FIG. 2 is an explanatory view of a wafer mark of FIG. 1;

FIG. 3 is an explanatory diagram of a light amount distribution on a pupil plane in FIG. 1;

FIG. 4 is an explanatory diagram of an illumination range on a wafer surface in FIG. 1;

FIG. 5 is an explanatory view of a stopper for the wafer mark of FIG. 1;

FIG. 6 is an explanatory diagram of diffracted light from a diffraction grating.

FIG. 7 is an explanatory view of the reference mark of FIG. 1;

FIG. 8 is a flowchart of the first embodiment of the present invention.

FIG. 9 is an explanatory diagram of a wafer mark position on a wafer surface.

FIG. 10 is an explanatory diagram of a wafer mark image of FIG. 1;

FIG. 11 is an explanatory diagram of a method of correcting a damascene amount when detecting the center position of a wafer mark according to the second embodiment of the present invention.

FIG. 12 is a schematic diagram of a main part of an optical system according to a second embodiment of the present invention.

FIG. 13 is an explanatory diagram of the wafer mark of FIG. 12;

FIG. 14 is an explanatory view of the reference mark of FIG. 12;

FIG. 15 is a flowchart of a second embodiment of the present invention.

FIG. 16 is an explanatory diagram of a wafer mark position on a wafer surface.

FIG. 17 is an explanatory diagram of the wafer mark image of FIG. 12;

FIG. 18 is a diagram illustrating a method of correcting a damascene amount when detecting the center position of a wafer mark according to the second embodiment of the present invention.

FIG. 19 is a schematic view of an optical system of a conventional positioning device.

20 is an explanatory diagram of the wafer mark of FIG. 19;

FIG. 21 is an explanatory diagram of a light amount distribution on a pupil plane in FIG. 19;

FIG. 22 is an explanatory view of the reference mark of FIG. 19;

FIG. 23 is a flowchart of the alignment method in FIG. 17;

FIG. 24 is a schematic cross-sectional view of a wafer coated with a resist.

FIG. 25 is an explanatory diagram showing a damascene amount at a center position associated with undulation of a wafer mark and a resist surface;

FIG. 26 is an explanatory diagram of another wafer mark according to the present invention.

FIG. 27 is an explanatory diagram of a method of correcting a damascene amount when detecting a center position using the wafer mark of FIG. 26;

FIG. 28 is an explanatory diagram of another wafer mark according to the present invention.

[Explanation of symbols]

 R Reticle W Wafer GW, MW Wafer mark GS, MS Reference mark 1 Projection lens IL Illumination system 2 He-Ne laser 5, 10 Polarization beam splitter 6 λ / 4 plate 7, 9 Lens 8 Mirror 11 Receiving means (CCD) 12 LED Ma Alignment mark Ma1-Ma3, MW1-MW3 Alignment mark 25 Stopper 30 Stopper control device

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-54918 (JP, A) JP-A-2-206706 (JP, A) JP-A-4-186717 (JP, A) JP-A-2-206 157844 (JP, A) JP-A-4-303914 (JP, A) JP-A-4-303915 (JP, A) JP-A-2-54103 (JP, A) JP-A-1-230233 (JP, A) JP-A-4-186716 (JP, A) JP-A-1-40491 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01L 21/027

Claims (7)

(57) [Claims] 1. A positioning apparatus for arranging a receiving means synchronized with a reticle and a wafer via an optical system and performing relative positioning between the receiving means and the wafer, wherein a plurality of lines having different line widths are provided on the wafer surface. A plurality of wafer marks each composed of an alignment mark are formed, and a resist is applied on the surface thereof. A change in the incident position of the light beam to the receiving means due to the line width of the alignment mark and the undulating shape of the resist surface. Recording means for recording a relational expression with a displacement amount of position measurement by the optical system, a plurality of alignment marks forming the wafer mark illuminated by the illumination system are simultaneously recorded on the receiving means surface by the optical system. Or, the light is guided at a time interval, and the receiving unit extracts the position information of the plurality of alignment marks simultaneously or at a time interval, and extracts this information to the plurality of wafer marks. Then, using the positional information obtained at this time and the relational expression recorded in the recording means, a positional deviation error caused by the unevenness of the resist surface is statistically obtained, and the positional deviation error is referred to. A positioning apparatus, wherein relative positioning between the wafer and the receiving means is performed. 2. The alignment apparatus according to claim 1, wherein said plurality of alignment marks are formed of diffraction gratings and are arranged in the same direction as or orthogonal to the alignment direction. 3. One of the plurality of alignment marks.
2. The alignment apparatus according to claim 1, wherein a plurality of alignment marks have the same line width and are arranged at the same pitch in the alignment direction. 4. A method of optically detecting the positions of a plurality of relief marks on a resist-coated wafer, and aligning a pattern on the wafer with a circuit pattern of a mask based on the position detection; In an exposure apparatus for exposing a resist covering a pattern on the wafer via the circuit pattern, the plurality of relief-shaped marks form first and second alignment patterns each having a different line width w ₁ and w _2. And optically detecting the positions of the first and second alignment patterns of one of the plurality of relief marks at the same time or at a time interval. position data x _1, means allowed to generate x _2, the line width and the position data of the first alignment pattern (w _1, x _1), the line width and position data of the second alignment pattern (w _2, Performed on a relief-like mark the plurality of that seek function x (w) of the line width w, to determine the position data x ₀ when the line width w = 0 by the function number x (w) based on the ₂₎ Means for performing the alignment based on statistical values of a plurality of position data obtained at this time. 5. A method for optically detecting positions of a plurality of relief marks on a resist-coated wafer, and aligning a pattern on the wafer with a circuit pattern of a mask based on the position detection. Exposing a resist covering the pattern on the wafer through the circuit pattern, and then developing the resist on the wafer to produce a semiconductor device from the wafer; Of the plurality of linear patterns of one of the relief-shaped marks.
_1, first with w _2, the respective position of the second alignment pattern optically detected apart simultaneously or temporally, the first position corresponding to the first alignment pattern on the basis of the position detection the second form position data x ₂ corresponding to the data x ₁ and the second alignment pattern, the line width and position data of the first alignment pattern (w _1, x ₁₎ and the second alignment pattern Line width and position data (w ₂ , x ₂ )
And a function x (w) of the line width w is calculated based on
(W) determining the position data x ₀ when the line width w = 0 is performed for the plurality of relief-shaped marks, and the positioning is performed based on the statistical values of the plurality of position data obtained at this time. A method of manufacturing a semiconductor device. 6. An exposure apparatus according to claim 4, wherein said relief mark comprises a diffraction grating. 7. The method according to claim 5, wherein said relief mark comprises a diffraction grating.